Corals, Worms, etc. 



itself on to the tips of its rays so that its body is strongly 

 arched or humped. Next it applies its many tube feet to 

 the sides of either valve and pulls strongly and steadily at 

 right angles to their surfaces. Eventually the valves 

 separate ever so little and the starfish turns its stomach 

 inside out, a feat it can accomplish without difficulty, 

 inserts it between the valves and sucks out the unfortunate 

 mollusc. 



Experiment has shown that the valves of a healthy 

 mussel can withstand a sudden pull of 4000 grammes, but 

 -that they will yield to a continued pull of 900 grammes. 

 Seeing that the starfish can exert a continued pull of 1350 

 grammes, it is hardly surprising that it never goes hungry. 

 A fight between a starfish and a sea-urchin is an exciting 

 yet frequent event. 



The sea-urchin, sometimes called the sea-hedgehog, is, 

 as its popular name implies, densely studded with spines 

 of various sizes. Each spine is attached to the body of 

 the urchin by a ball-and-socket joint and is therefore 

 freely movable. Despite its formidable armour, the 

 urchin is no match for the starfish, which simply lays one 

 of its rays upon the urchin and holds on as tightly as it 

 can with its tube feet. The urchin replies by biting its 

 adversary vigorously, and the starfish replies by removing 

 its ray and tearing off several of the urchin's spines as it 

 does so. This performance on the part of the starfish is 

 repeated again and again, till the urchin is denuded of 

 its armour, when the starfish, with its uncanny elastic 

 stomach, sucks out the vitals of its victim. One would 

 think that the starfish suffers somewhat in these conflicts. 

 Probably this is the case, but it is of little moment, for the 

 starfish is so highly imbued with the power of regenera- 

 tion that one of its rays, torn from the rest, will eventually 

 grow into a new starfish. 



The power of regeneration reaches an extraordinary 

 degree of development in a minute, trumpet-shaped 

 animal known as Stentor, which lives affixed to water weed 



291 



